This invention relates to antifriction bearings and more particularly to a bearing assembly in which the rolling elements are arranged in two rows and are preset.
The tapered roller bearing has the capacity to carry heavy radial loads--and in that sense possesses the advantages of a cylindrical roller bearing--but unlike a cylindrical roller bearing, it possesses the further capacity to take heavy axial loads. It thus finds wide-spread use in machinery. Typical of such machinery are transmissions.
In its simplest form an antifriction bearing, whether it be a tapered roller bearing, an angular ball bearing or merely a cylindrical roller bearing, has an outer race, an inner race, some type of rolling elements arranged in a row between the races, and usually a cage or retainer to maintain the proper spacing between the rolling elements. Normally the outer race fits into a housing bore with one of its end faces against a shoulder in that bore, whereas the inner race fits over a shaft with one of its end faces against a flange or shoulder on the shaft or at least against some type of annular abutment that is along the shaft.
The tapered roller bearing lends itself to more complex configurations which are in essence combinations of single row bearings. For example, when two single row tapered roller bearings are oriented with their rollers in opposition, the overall assembly will accommodate axial loads in both directions. Of course, an axial load that is transmitted through a tapered roller bearing assembly must be transferred from the bearing assembly to the housing and likewise from the bearing assembly to the shaft, and various devices have been developed to effect this transfer--shoulders or abutments at the ends of the bearing assembly being the most common.
Sometimes it is more convenient to form a part with a simple through bore for holding the bearing. But a through bore will not in and of itself stabilize the bearing axially, that is accommodate axial loads. The Timken Company manufactures a single row tapered roller bearing which possesses a radially outwardly directed flange on its outer race, more commonly referred to as the cup, and this flange may be clamped against the end face of a housing containing a through bore, with the remainder of the cup located in the through bore. The flange, being solidly clamped against the housing, prevents the race from moving axially in the through bore.
In one type of truck transmission the output shaft is carried by two single row tapered roller bearings mounted in opposition--indeed in the indirect or X condition (FIG. 1). As such, the small diameter ends of the tapered rollers for the two rows are presented toward each other. Whereas the cones of the two bearings fit around the output shaft, the cups fit into a through bore in an end wall of the transmission case, and to facilitate assembly, the cups are often loose in the sense that no interference exists between the cup and the through bore. The cup on one of the bearings has a flange which is clamped against the end face of the wall through which the through bore passes. The cones, on the other hand, are clamped together on the shaft. Being mounted in opposition, the two bearings may be adjusted against each other to control the axial and radial clearance within the bearing, and this adjustment is derived from spacers which are between the two cups and the two cones. In this regard, the spacer between the two cones is a simple sleeve that is clamped up between those cones. It is normally not hardened. The spacer between the cups is somewhat more complex in that it has an annular oil groove and radially directed holes to admit oil from the groove to the space between the two bearings. It may or may not be hardened.
From the standpoint of manufacturing, the spacer located between the cups must be machined on its inner diameter, on its outer diameter and on both of its end faces. Also, an annular groove and radial oil holes must be added. Furthermore, the spacer must be hardened if the application requires it and, all surfaces must be ground. The cup spacer is a component in the current assembly which must be maintained in inventory by the bearing manufacturer for use when the bearing components are matched to obtain the proper bearing setting at the manufacturer's assembly area. With the current cup spacer, there are two possible wear surfaces--one along the conventional cup and the other along the flanged cup. In addition, the minimum overall width of the current bearing assembly is limited by the minimum cup spacer width which is dictated by the required annular groove and oil hole diameter.
The present invention eliminates many of the aforementioned concerns about the current bearing assembly. The invention resides in a bearing assembly which supports a shaft in the bore of a housing. The bearing assembly includes two single row bearings, each of which is capable of supporting axial as well as radial loads, and these bearings are mounted in opposition to each other. One of the bearings is conventional. The other has an integral extension at its one end, and that extension extends to and abuts the outer race of the conventional bearing to maintain the proper spacing between the two outer races. Indeed, the extension serves to maintain the proper spacing between the raceways of the two outer raceways, and in that sense replaces the cup spacer of a conventional bearing assembly. The invention also resides in the combination of the bearing assembly, a shaft and a housing, and in the unique bearing which forms part of the assembly.